Numerous processes are within the purview of those skilled in the art for the preparation of toners. Emulsion aggregation (EA) is one such method. Emulsion aggregation toners may be used in forming print and/or electrophotographic images. Emulsion aggregation techniques may involve the formation of a polymer emulsion by heating a monomer and undertaking a batch or semi-continuous emulsion polymerization, as disclosed in, for example, U.S. Pat. No. 5,853,943, the disclosure of which is hereby incorporated by reference in its entirety. Emulsion aggregation/coalescing processes for the preparation of toners are illustrated in a number of patents, such as U.S. Pat. Nos. 5,290,654, 5,278,020, 5,308,734, 5,344,738, 6,593,049, 6,743,559, 6,756,176, 6,830,860, 7,029,817, and 7,329,476, and U.S. Patent Application Publication Nos. 2006/0216626, 2008/0107989, 2008/0107990, 2008/0236446, and 2009/0047593. The disclosures of each of the foregoing patents are hereby incorporated by reference in their entirety.
Polyester EA ultra low melt (ULM) toners have been prepared utilizing amorphous and crystalline polyester resins as illustrated, for example, in U.S. Patent Application Publication No. 2008/0153027, the disclosure of which is hereby incorporated by reference in its entirety.
Many polymeric materials utilized in the formation of toners are based upon the extraction and processing of fossil fuels, leading ultimately to increases in greenhouse gases and accumulation of non-degradable materials in the environment. Furthermore, current polyester based toners may be derived from a bisphenol A monomer, which is a known carcinogen/endocrine disruptor.
Bio-based polyester resins have been utilized to reduce the need for this carcinogenic monomer. An example, as disclosed in co-pending U.S. Patent Application Publication No. 2009/0155703, includes a toner having particles of a bio-based resin, such as, for example, a semi-crystalline biodegradable polyester resin including polyhydroxyalkanoates, wherein the toner is prepared by an emulsion aggregation process.
In order to emulsify conventional and bio-based polymers utilized in the EA process, the acid functionality of the polyester is often increased, as measured by acid value. This is done by adding a polyfunctional monomer, such as trimellitic anhydride (TMA), post polymerization, so that the hydroxyl (OH) terminal groups are converted into carboxylated (COOH) groups. For example, isosorbide-based polyesters have limited reactivity at the isosorbide end groups, thereby restricting the conversion of OH groups into carboxylated end groups. The addition of a non-bio-based monomer, such as TMA, post-polyesterification, can enhance functionality of the polyesters so that emulsion-aggregation chemistry can be carried out.
Notwithstanding the foregoing, alternative, cost-effective, environmentally friendly toners remain desirable.